U.S. patent number 5,052,391 [Application Number 07/601,150] was granted by the patent office on 1991-10-01 for high frequency high intensity transcutaneous electrical nerve stimulator and method of treatment.
This patent grant is currently assigned to R.F.P., Inc.. Invention is credited to Michael E. Halleck, Leon M. Silberstone.
United States Patent |
5,052,391 |
Silberstone , et
al. |
October 1, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
High frequency high intensity transcutaneous electrical nerve
stimulator and method of treatment
Abstract
A transcutaneous electrical nerve stimulation (TENS) device
provides significantly improved patient results by supplying high
frequency electrical pulses at frequencies in a range of 2.5 to 60
kilohertz. The frequency and intensity of the pulses can be
adjusted, to treat the patient at the optimal frequency and
amplitude in order to treat chronic or acute pain or to block the
pain caused by a traumatic or medical procedure. Starting at a
mid-level of intensity where no stimulation occurs, the frequency
is adjusted downwardly until there is some nerse sensation. At this
point, the procedure may be performed while the frequency is
adjusted downwardly as needed to maintain nerve sansation. The wave
form characteristic of the pulses is an AC wave form with a square
wave portion with rapid rise time and slower fall time followed by
a pulse portion of the opposite polarity compared to the square
wave portion.
Inventors: |
Silberstone; Leon M. (LaJolla,
CA), Halleck; Michael E. (Longmont, CO) |
Assignee: |
R.F.P., Inc. (Aurora,
CO)
|
Family
ID: |
24406427 |
Appl.
No.: |
07/601,150 |
Filed: |
October 22, 1990 |
Current U.S.
Class: |
607/46; 607/66;
607/76 |
Current CPC
Class: |
A61N
1/36021 (20130101); A61N 1/06 (20130101) |
Current International
Class: |
A61N
1/36 (20060101); A61N 001/34 () |
Field of
Search: |
;128/419R,421,422
;600/27 ;606/32,40,52 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Holland & Hart
Claims
The invention claimed is:
1. A method for blocking the pain caused by a traumatic or medical
procedure on a patient with the use of transcutaneous electrical
nerve stimulation, comprising the steps of:
(a) generating a series of electrical pulses at a frequency in the
range of 2.5 to 60 kilohertz;
(b) applying said generated electrical pulses to a desired area on
a patient's body;
(c) electrically conducting the applied electrical pulses through
the patient's body to stimulate selected nerves; and
(d) performing the procedure.
2. A method as defined in claim 1 wherein generating the series of
electrical pulses includes:
generating the electrical pulses with an electrically powered
stimulator; and
electrically isolating the patient from the stimulator.
3. A method as defined in claim 2 wherein electrically isolating
the patient from the stimulator comprises coupling a signal
generated by the stimulator through a transformer to the
patient.
4. A method as defined in claim 1 wherein the generating step
further comprises adjusting the frequency of the electrical pulses
within said range.
5. A method as defined in claim 4 further comprising adjusting the
high frequency electrical pulses to 60 kilohertz.
6. A method as defined in claim 4 wherein generating the series of
electrical impulses further comprises adjusting the intensity of
the electrical pulses.
7. A method as defined in claim 6, further comprising the
additional steps of:
(e) adjusting the frequency to the highest frequency within the
frequency adjustment range;
(f) adjusting the intensity to the lowest intensity within the
intensity adjustment range; then
(g) adjusting the intensity to a level which is slightly below that
level which achieves perceptible nerve sensation to the
patient;
(h) adjusting the frequency downward from the highest frequency to
a relatively lower frequency until the patient begins to perceive a
nerve sensation; and
(i) continuing to adjust the frequency downwardly as necessary
throughout the procedure to maintain the nerve sensation.
8. A method as defined in claim 1 further including forming the
high frequency electrical pulses to include a square wave portion
and an opposite polarity pulse centered about a zero reference
potential.
9. A method as defined in claim 8 further comprising forming the
square wave portion with a leading edge having a relatively rapid
rise time and with a trailing edge having a relatively slower fall
time.
10. An apparatus for blocking the pain caused by a traumatic or
medical procedure on a patient with the use of transcutaneous
electrical nerve stimulation, comprising:
source means for supplying a source of relatively high DC
voltage;
voltage control means connected to said source means and receptive
of the relatively high DC voltage and operative for supplying a
controllable level of the DC voltage;
an output transformer means having a primary and a secondary
winding, the primary winding connected to said voltage control
means and receptive of the controlled DC voltage level supplied by
said voltage control means, the transformer means operatively
inducing in the secondary winding an electrically isolated output
signal of approximately the same frequency as the signal in the
primary winding and with an amplitude characteristic proportional t
the amplitude characteristic of the signal in the primary
winding;
oscillator means operative for generating a square wave oscillator
signal;
power driver means connected to the other end of said primary
winding of said output transformer means, the power driver means
receptive of said square wave oscillator signal and operative for
switching current through the primary winding at a frequency
related to the frequency of the oscillator square wave signal;
the secondary winding of said transformer means supplying an output
signal in response to the conduction of the power driver means, the
output signal being a wave form which includes a square wave
portion of one polarity having a leading edge with a relatively
rapid rise time and a trailing edge with a relatively slower fall
time and a pulse portion of the opposite polarity; and
a pair of electrodes connected to the secondary winding of said
output transformer means for conducting the output signal to the
skin of a patient.
11. Apparatus as defined in claim 10, further comprising:
adjustment means connected to said oscillator means and operative
for adjusting the frequency of the oscillator square wave
signal.
12. Apparatus as defined in claim 11, further comprising:
adjustment means connected to said voltage control means and
operative for adjusting the level of the controlled voltage.
13. Apparatus as defined in claim 11 wherein said square wave
oscillator signal is adjustable within a range of 2.5 kilohertz to
60 kilohertz.
14. Apparatus as defined in claim 10 wherein the power driver means
conducts current through the primary winding during one state of
the square wave oscillator signal and does not conduct current
through the primary winding during the other state of the square
wave oscillator signal, and said square wave signal has a
predetermined frequency within the range of 2.5 kilohertz to 60
kilohertz.
15. Apparatus as defined in claim 14 further comprising:
a second pair of electrodes connected in parallel with said first
electrodes.
16. Apparatus as defined in claim 14 further comprising:
a first output channel comprising the source means, the voltage
control means, the output transformer means, the oscillator means,
the power driver means, and the pair of electrodes, all as first
aforesaid; and
a second output channel comprising the first said source means, a
second said voltage control means, a second said output transformer
means, a second said oscillator means, a second said power driver
means, and a second pair of electrodes.
17. A method for blocking the pain caused by a traumatic or medical
procedure on a patient with the use of transcutaneous electrical
nerve stimulation, comprising the steps of:
(a) generating a high frequency series of electrical pulses;
(b) adjusting the frequency of the pulses to a relatively high
rate;
(c) adjusting the intensity of the pulses to a relatively low
level;
(d) applying said generated pulses to a desired area on a patient's
body;
(e) adjusting the intensity of the pulses to a desired level;
(f) adjusting the frequency of the pulses to a relatively lower
frequency until the patient begins to perceive a nerve sensation;
and
(g) continuing to adjust the frequency downwardly as necessary
throughout the procedure to maintain the nerve sensation.
18. A method as defined in claim 17 wherein the high frequency
electrical pulses can be adjusted within the frequency range of 2.5
to 60 kilohertz.
19. A method as defined in claim 17 further including forming the
high frequency electrical pulses to include a square wave portion
and an opposite polarity pulse centered about a zero reference
potential.
20. A method as defined in claim 19 further comprising forming the
square wave portion with a leading edge having a relatively rapid
rise time and with a trailing edge having a relatively slower fall
time.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to transcutaneous electrical nerve
stimulation and more particularly to a new and improved apparatus
and process of applying relatively high frequency and high
intensity pulses of electrical energy to the skin of a patient in
order to obtain improved medical results such as blocking pain for
a traumatic or medical procedure.
2. Description of the Prior Art
Transcutaneous electrical nerve stimulation (TENS) is a well known
medical treatment used for symptomatic relief and management of
chronic intractable pain, and as an adjunctive treatment in the
management of post surgical and post traumatic acute pain. TENS
involves the application of electrical pulses to the skin of a
patient. Electrodes are located at selected locations on the
patient's skin and the electrical energy is transferred between the
two electrodes. The electrical energy is usually applied in the
form of mild, electrical impulses. The impulses pass through the
skin and interact with the nerves that lie underneath the skin. The
electrical impulses act on the nervous system in such a way as to
suppress the sensation of pain that would otherwise serve as a
protective mechanism. As a symptomatic treatment, TENS has proven
to effectively reduce pain for patients suffering from chronic or
acute pain. TENS has no capacity for curing the cause of the pain,
but simply interacts with the nervous system to suppress or relieve
the pain.
The typical TENS system includes the TENS stimulator, lead wires
and electrodes which are connected to the skin of the patient. The
TENS stimulator is, in effect, an electrical pulse generator which
delivers the electrical pulses or impulses at a predetermined fixed
or selectable frequency. Typical prior TENS frequency treatment
ranges have been in terms of hundreds of pulses per second. In many
cases, the treatment frequency is fixed by the design of the
electrical pulse generator, or is established as a preselected,
generally arbitrary rate at the time of treatment. Most typical
TENS pulse generators allow adjustment of the intensity or
amplitude of the pulses delivered. The typical intensity ranges in
the neighborhood of less than 100 volts peak to peak. The
electrical impulses applied have taken a variety of different
forms. For example, symmetrical sinusoidal wave forms, symmetrical
biphasic wave forms and DC needle spikes have all been applied in
various TENS treatments. Each of the wave forms are believed to
offer some advantage, although there has been no clear previous
consensus that any particular type of wave form is more
advantageous than another type.
Furthermore, the prior TENS has typically been used for pain
reduction rather than as an analgesic or painblocker in order to
allow the performance of a traumatic or medical procedure upon a
patient and there has been a long felt need for an analgesic or
pain-blocker for certain medical procedures. For example, the use
of electrolysis to remove hair from a patient's upper lip typically
is painful to a patient and causes swelling. It is typical for a
patient to only be able to tolerate from a few seconds to several
minutes of electrolysis. Similarly, pain, discomfort and anxiety
are common in electrolysis for hair removal in many anatomical
sites in the human body.
It is against this background information, and other information,
that the present invention has resulted.
SUMMARY OF THE INVENTION
A number of significant improvements and advancements in the field
of electrolysis and surgery are available as a result of the
present invention. Many traumatic or medical procedures which would
typically produce pain and swelling in the skin of a patient can be
performed with the use of the TENS device of the present invention.
These significantly improved medical results are obtained by
applying the TENS electrical impulses at substantially higher
frequencies than have previously been used or recognized. In
addition, the high frequency of the TENS impulses is adjusted or
selected for optimal medical results. Further, each electrical
impulse is preferably of a predetermined wave form characteristic
which is believed to substantially increase and enhance the TENS
effect and reduce swelling. Many other improvements will be
apparent and discovered upon full comprehension and application of
the aspects of this invention.
In accordance with one of its aspects, the present invention
pertains to a method of TENS stimulation in which a relatively high
frequency, preferably in the neighborhood of between 2.5 kilohertz
and 60 kilohertz, is applied to the patient. For reasons not fully
understood at the present time, the relatively higher frequency
seems to stimulate an increased TENS effect with reduced
swelling.
In accordance with another of its aspects, the present invention
allows the relatively high frequency of impulses to be selected to
optimize the relief obtained by the patient. The method involved is
to initially apply the impulses at the high end of the high
frequency range and at the low end of the amplitude or intensity
range. The amplitude of the electrical impulses is adjusted to a
level for the particular TENS treatment session, preferably at a
mid-level. The frequency is then selectively decreased in order to
maximize the stimulation effect until the patient senses a motor
nerve response or "tingling". By adjusting both the intensity and
the frequency in this manner, the treatment is optimized for each
patient.
According to a further aspect of the present invention, the
electrical impulse to the patient is preferably an AC wave form
which includes a square wave portion forming the first positive
half cycle of the AC wave form followed by a generally negative
rounded pulse portion forming the negative half cycle of the AC
wave form. The square wave portion is characterized by a relatively
fast rise time, a sustained or slightly decreasing amplitude level
over the majority of the time of the square wave portion and a
slower fall time. The fall time slope generally characterizes the
initial significant portion of the negative rounded pulse portion.
The negative portion thereafter returns to the baseline to commence
another AC wave form repetition. The energy within the positive
going square wave and the negative rounded wave is generally equal,
thereby transferring a zero net DC charge to the patient.
A more complete understanding and appreciation of the present
invention can be obtained by reference to the accompanying
drawings, which are briefly described below and from the detailed
description of a presently preferred embodiment, and from the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a generalized illustration of the method of treating a
patient with TENS, using a TENS stimulator connected to at least
one pair of electrodes attached to the skin of the patient.
FIG. 2 is a block diagram of one embodiment of the TENS stimulator
which may be used as shown in FIG. 1.
FIG. 3 is a block diagram of an output portion of the TENS
stimulator shown in FIG. 2, illustrating an alternative embodiment
providing two output channels driven by a single power driver.
FIG. 4 is a block diagram of another embodiment of the TENS
stimulator, providing two separate output channels, each of which
is driven by its own power driver.
FIG. 5 is a schematic circuit diagram of the stimulator in FIG. 2,
which is duplicated for each output channel of the TENS stimulator
shown in FIG. 4.
FIGS. 6A and 6B are diagrams of a single pulse of a repetitive AC
output wave form supplied by the TENS stimulator shown in FIGS. 2
and 4.
DETAILED DESCRIPTION
The treatment of a human patient 10 with a TENS unit in accordance
with the present invention is illustrated in FIG. 1. Lacerations 11
requiring sutures are shown on the patient 10. A pair of
conventional electrodes 12 and 14 are attached to the patient's
skin in a predetermined location adjacent one of the lacerations 11
to alleviate or block pain so that sutures may be applied with
little or no pain to close the laceration. The electrodes 12 and 14
are respectively connected by conductors 16 and 18 to a TENS
stimulator 20. Pulses of electrical energy are delivered through
the conductors 16 and 18 to the electrodes 1 and 14, where they are
conducted into the skin to stimulate the nerves and achieve a TENS
medical effect.
Preferably the TENS stimulator of the present invention provides
two output channels for stimulating two separate areas of the
patient 10. For example, the TENS stimulator 20 has one output
channel to which the electrodes 12 and 14 and the conductors 16 and
18 are connected. A second output channel connects electrodes 22
and 24 by conductors 26 and 28, respectively, to the TENS
stimulator. It has been determined that in some acute pain
situations, the application of two separate TENS impulses between
two pairs of electrodes is very effective in stimulating favorable
patient treatment.
A single channel TENS stimulator 30 is illustrated in FIG. 2. The
stimulator 30 includes a power supply 32 which preferably takes the
form of a rechargeable battery. The battery is connected by a
switch 34 to a DC inverter 36. The DC inverter converts the
relatively lower DC voltage level of the battery power supply 32 to
a relatively higher DC level and applies that higher DC level at 38
to a voltage control 40. A potentiometer 42 controls the voltage
control 40 to adjust the output voltage at 44 between ground
reference and the maximum voltage at 38 The voltage at 44 is
applied to a primary winding 46 of an output transformer 48.
Current is conducted through the primary winding 46 by a power
driver 50 connected to the other terminal of the primary winding
46. Signals 52 from an oscillator 54 control the power driver 50.
Preferably the signals are square wave signals supplied by the
oscillator 54, and the power driver 50 responds to the square wave
signals by conducting current through the primary winding 46 in
relation to the on times of the square wave signal 52. A
potentiometer 56 adjusts the frequency of the oscillator 54.
Output signals are derived by the secondary winding 58 of the
transformer 48. The output signals are supplied on the electrodes
16 and 18, for example, to the patient electrodes 12 and 14 (FIG.
1). Use of the output transformer 48 effectively supplies the
output pulses centered relative to ground level, and thereby
transfers a zero net DC charge to the patient.
Use of the voltage control 40 to control the level of DC voltage at
44, by use of the potentiometer 42, establishes the intensity or
amplitude of the output signal applied from the secondary winding
58 of the transformer 48. The power driver 50, as will be explained
in greater detail below, essentially conducts the amount of current
established by the potential at 44 through the primary winding. The
potentiometer 56 controls the frequency of the oscillator 54 to
thereby control the frequency of pulses delivered from the output
transformer 48. Of course, in place of the potentiometers 42
(intensity) and 56 (frequency) any other suitable means for control
may be substituted, such as digitally controlled potentiometers
working in conjunction with a microprocessor. A microprocessor
might further be utilized in the present invention to drive
displays of the frequency and intensity information.
The relative size of the battery of the present invention is
significantly larger than most batteries of TENS devices which are
adapted to be worn by the patient Due to the relatively high
electrical power requirements which have been determined to be
desirable for TENS treatment, the power supply 32 should be a
relatively large battery capable of being recharged. Considerable
electrical power is consumed by the relatively high energy pulses
created by the voltage level at 44 and switched through the primary
winding 46 by the power driver 50.
In another embodiment of the TENS stimulator, a single output
transformer 48 and power driver 50 are used in a TENS stimulator to
obtain two output channels, as is shown in FIG. 3. The remainder of
the circuit not shown in FIG. 3 is the same as that described in
conjunction with FIG. 2. As can be appreciated, two conductors 16
and 26 are connected to one end of the secondary winding 58 and
another pair of conductors 18 and 28 are connected to the other end
of the secondary winding 58 of the output transformer 48. The
single output signal developed across the output winding 58 is thus
applied to each separate pair of conductors 16, 18 and 26, 28.
While the arrangement shown in FIG. 3 has the advantage of cost
reduction, it does reduce the magnitude of the signals applied on
the conductor pairs 16, 18 and 26, 28 by an equal amount, since the
conductor pairs are connected in parallel to separate parallel
impedances through the patient Thus, equal intensities or voltages
of output signals are applied on both of the conductor pairs 16, 18
and 26, 28.
A third embodiment 60 of the TENS stimulator, which allows true
independent control over the output signal pulses delivered over
two separate output channels, is illustrated in FIG. 4. A single
power supply and DC inverter 36 are used, and the remainder of the
components are essentially duplications of those described in
conjunction with the TENS stimulator 30 shown in FIG. 2. As such,
the duplicated components for one channel are labeled with
reference numerals ending in a subscript a, and those duplicated
components used in the second channel are labeled with reference
numbers ending in a subscript b. In all regards, each of the
channels in the TENS stimulator 60 operate similarly and in the
manner previously described in conjunction with the TENS stimulator
30 shown in FIG. 2.
It should be noted that the magnitude of the output signal pulses
from secondary windings 58a and 58b of transformers 48a and 48b are
separately and independently adjustable by the potentiometers 42a
and 42b, respectively. Similarly, the frequency of application of
the output pulses from the two channels are separately and
independently adjustable by the potentiometers 56a and 56b. Thus,
the output signal pulses supplied by each channel are separately
controllable and adjustable in frequency and amplitude for each
channel.
The TENS stimulator 30, and the essential portions duplicated to
obtain the TENS stimulator 60 shown in FIG. 4, are shown in greater
detail in schematic form in FIG. 5.
The power supply 32 includes a conventional rechargeable battery
62. In addition, charging jacks 64 are connected by diode 66 across
the battery 62. The charging jacks 64 will be utilized either to
power the TENS stimulator 30 from a conventional DC power supply
which may be driven by AC power, or to charge the rechargeable
battery 62. An LED 68 is also provided to indicate the application
of power at the charging jacks 64. Power from the power supply 32
is connected by the switch 34 to the DC inverter 36. Another LED 70
is provided to signal the operation of the TENS device when the
switch 34 is closed A variety of different circuits for the power
supply can be employed.
The DC inverter 36 utilizes a conventional DC inverter integrated
circuit (IC) 72. The IC 72 is connected in the conventional manner
illustrated. An inductor 74 is connected between two terminals of
the IC 72, and switching currents therethrough develop relatively
high voltage spikes. The resulting high voltage spikes are
rectified by a diode 76. The rectified spikes charge a relatively
high capacity filter capacitor 78. The maximum DC voltage level
signal 38 is available between the terminals of the filter
capacitor 78. Feedback resistors 80 and 82 supply a feedback signal
to the IC 72 for the purpose of regulating the output voltage to
the fixed maximum level. Preferably the ICU 72 is a commercial
part, Motorola No. MC34063P1. Preferably the inductor 74 is a 200
microhenry, 1.5 amp component. A variety of different circuits for
the inverter 36 can be employed.
The voltage control 40 receives the maximum DC output signal 38.
The voltage control 40 includes a biasing transistor 84 and a
regulating transistor 86. The base of the biasing transistor 84 is
connected to the potentiometer 2. The voltage level from the
potentiometer 42 establishes the conductivity of the biasing
transistor 84. The level of conductivity of the biasing transistor
84 establishes the signal applied to the base of the regulating
transistor 86, thereby causing transistor 86 to regulate the output
voltage at 44 to a predetermined level established by the
potentiometer 42. A resistor 88 in series with the emitter of the
regulating transistor 86 further limits the amount of current drawn
from the filter capacitor 78 through the primary winding 46 of the
output transformer 48. A number of alternative circuits for the
voltage control can be employed.
The oscillator 54 is of a conventional configuration which utilizes
an operational amplifier 90 in conjunction with a feedback network
which includes the potentiometer 56 and a capacitor 92 connected to
its input terminal. The output signal 52 from the oscillator 54 is
substantially a square wave having a frequency established by the
resistance of the potentiometer 56 in the feedback network
connected to the input terminal of the operational amplifier 90. A
variety of other conventional square wave oscillator circuits can
be employed
The square wave signal 52 is applied to the power driver 50. The
power driver 50 includes a first switching transistor 94 which
receives the square wave signal 52 at its base terminal. When the
square wave signal 52 is high, the switching transistor 94 is
conductive and a positive signal is developed across resistor 96.
The positive signal across resistor 96 is applied to the base
terminal of a power switching transistor 98 to render it
conductive. When conductive, the power switching transistor 98
conducts current through the primary winding 46 of the output
transformer 48. When the square wave signal at 54 is low, the
transistors 94 and 98 are non-conductive. A number of different
types of power driver circuits 50 could be employed, but, as will
be described below, the power driver circuit 50 should preferably
retain the capability to achieve the desirable characteristics of
the output wave form.
The amount of energy conducted through the primary winding 46 is
determined in large measure by the voltage level at 44, which is
developed by the regulating transistor 86, and by the magnitude of
the current conducted through the primary winding as controlled by
the regulating transistor 86. Thus, the voltage control essentially
controls the intensity of the treatment the patient receives, while
the power driver actually develops the signals applied to the
patient by switching signals through the primary winding 46 of the
transformer 48. The signal in the primary winding 46 establishes
the maximum intensity or amplitude of the output signal induced in
the secondary winding 56 of the output transformer 48. Of course,
increasing the frequency of the square wave pulses 52 from the
oscillator 54 thereby controls the frequency of the electrical
impulses delivered from the TENS stimulator 30. Changing the
frequency of the output pulses does not significantly change the
magnitude of the energy delivered to the patient.
FIGS. 6A and 6B illustrate the signal characteristics of an output
pulse wave form 100 provided at the secondary winding 56 of the
output transformer 48. FIG. 6A exemplifies the output pulse wave
form delivered into a 500 ohm resistive load, while FIG. 6B
exemplifies the output wave form delivered to a 10,000 ohm
resistive load.
The wave form 100 shown in FIG. 6A is centered about a zero
reference potential or base line. Centering the wave form 100 is
attained by the inherent functionality of the output transformer
48. As a result of this centering, the amount of charge transferred
during a first half cycle, represented by that square wave portion
above the zero reference, and the amount of charge transferred
during a second half cycle portion, represented by the negative
rounded pulse portion below the reference line, are equal.
Therefore, a zero net charge transfer to the patient occurs.
As will be noted by comparing FIG. 6A and 6B, the first positive
square wave portion of each wave form is essentially the same. This
positive portion is characterized generally as a square wave having
a relatively rapid rise time, or leading edge, shown at 102, a
relatively constant or slightly decreasing maximum value at 104
which is sustained during the majority of the time that the
positive portion occurs, and by a relatively slower fall time, or
trailing edge, shown at 106. The amount of decrease at 104 depends
substantially on the resistive component of the load between the
electrodes (FIG. 1) attached to the patient's body, with greater
resistances achieving lesser reductions or decreases.
The slope of the trailing edge 106 continues into the negative
portion and may continue to curve in various configurations shown
at 108 when another output pulse 100 is generated by the TENS
stimulator 30. The ending curve of the negative portion is
characterized by a relatively rapid rise time of the same slope as
the leading edge 102 of the positive square wave portion.
The relatively rapid rise time and relatively slower fall time of
the output wave form are achieved as a result of the inherent
collector to base capacitance in the power switching transistor 98,
shown in FIG. 5. This capacitance allows the collector voltage of
the power switching transistor 98 to rapidly change, thereby
inducing a high charging current in the primary winding. However,
after this inherent base to collector capacitance has been charged
during the time that the power switching transistor 98 is
conductive, the current flow through the secondary winding is
relatively more slowly terminated when the power switching
transistor 98 becomes nonconductive. Thus, the relatively slower
fall time (106, FIGS. 6A and 6B) is created in the output pulse.
During the mid-region -04 of the square wave portion, the current
flow through the primary winding increases at a relatively uniform
rate to obtain the sustained output voltage at 104.
For reasons which are not readily understood at the present time, a
square wave portion having the relatively rapid rise time and the
relatively slower fall time seems to provide an additional
beneficial effect in patient treatment using TENS. It appears as
though the significant aspects of the square wave which give rise
to this improvement are the relatively rapid rise time and the
relatively slower fall time.
To utilize the TENS stimulator of the present invention on a
patient, the electrodes are attached to the patient and the
conductors connect the output terminals of the output transformer
48 to the electrodes. Prior to turning the power on, the frequency
potentiometer 56 is manually preset to provide the maximum output
pulse delivery frequency upon energization, which is preferably
about 60 kilohertz. The intensity potentiometer 42 is also manually
preset to provide a relatively low amplitude or intensity for the
output signal pulse upon energization. The switch 34 is then closed
to energize the circuit and the intensity potentiometer 42 is
adjusted to increase the amplitude or intensity of the output
signal pulses to a mid-level, or until the patient begins to
receive a sensation or tingling. Thereafter the frequency is
adjusted downwardly with the frequency potentiometer 56 from its
maximum level until the patient begins to sense a stimulation
caused by a lower frequency of application of electrical impulses.
Generally speaking the frequency at which the patient begins to
sense the application of electrical impulses is an optimum one for
that particular patient, and it will generally fall within the
range of 2.5 kilohertz to 60 kilohertz. The amount of the
stimulation should not be such as to induce pain, but should be a
relatively comfortable sensation.
At this time, the medical procedure, such as applying sutures or
performing electrolysis, may be performed. With time, the patient
may need to adjust the frequency downwardly from the previous level
to maintain the tingling sensation whereby there is an increase in
the level of analgesia produced. These rises in analgesia continue
throughout treatment in response to slight decreases in frequency.
This constant adjustment in frequency may be carried out by the
patient, by means of a hand-held remote control device (not shown)
that includes a button for easily decreasing the frequency as the
clinical sensation of tingling decreases. This control of pain
reduction by the patient is one of the theories proposed for the
efficacy of the present invention, since it removes the feeling of
"lack of control" in an environment associated with pain,
discomfort and anxiety.
By providing the independent adjustment of frequency, relatively
high frequency application of TENS to a patient is possible.
Furthermore, by adjusting the frequency of the TENS application
separately and particularly for each patient, the optimum TENS
treatment frequency for the patient may be obtained. However, the
frequency level is slowly and gradually adjusted throughout the
whole treatment session resulting in increased analgesia. The
application of the output pulse wave form having a square wave
positive portion with a relatively rapid rise time leading edge and
relatively longer fall time trailing edge, increases the effective
stimulation and treatment of the patient.
It is believed that the present invention obtains the desired
results due to the fact that the electrical impulses generated
thereby influence the nerve cells to produce natural substances
such as Beta-endorphins, GABA, norepinephrine, dopamine,
enkephalin, substance P and somatostatin, which produce analgesia
and inhibitory action on nociceptive dorsal horn neurons and
trigger reactions such as the secretion of serotonin, a naturally
occurring neurotransmitter which controls and raises the pain
threshold level. In addition, the electrical impulses may act to
block the natural nerve pain impulses travelling along A delta and
C delta nociceptive fine afferent nerve fibers. Thus, the treatment
of the present invention appears to be effective as a result of the
combination of blocking the pain impulses, triggering the reaction
of various naturally occurring body elements to increase analgesia
as well as raising the pain threshold and inhibiting cells in
important pain pathways in the spinal cord to the brian. Although
these are theories based on actual observations, the present
invention has proved effective in relief of chronic and acute pain
far in excess of prior TENS devices.
In an experimental treatment with the present invention used in
conjunction with electrolysis to remove facial hair on forty-two
patients, the following results were shown, as evaluated by the
patients themselves after orientation sessions describing how to
relay pain reduction during treatment. The patients had pain
reduction during treatment that ranged from fifty to one hundred
percent. Of the forty-two patients treated, only one had any signs
of slight swelling as a result of treatment which normally would
have resulted in swelling for all forty-two patients. Furthermore,
among patients too sensitive to tolerate more than a few minutes of
electrolysis without the present invention, it was possible to use
the TENS stimulator of the present invention for up to one hour of
electrolysis without pain, discomfort and anxiety, yet with a
feeling of complete relaxation for the patient. This lack of pain,
anxiety and adverse skin reaction continues for several hours after
the patient leaves the professional's office. Therefore, there is
no post operative pain, discomfort or swelling.
Presently preferred embodiments of the invention have been
described above with a degree of specificity. It should be
understood, however, that this description has been made by way of
preferred example and that the invention itself is defined by the
scope of the appended claims.
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